Bug 696557

Description:
In RHEL 6 host, boot up a RHEL 6.1 guest. Write a file in the guest, and save the md5 checksum of the file. Shut down the guest and do convert or snapshot and rebase operate. Boot up guest again and check the md5 value of the file. It changed.

Version-Release number of selected component (if applicable):
2.6.32-130.el6.x86_64
qemu-kvm:
rpm -qa|grep qemu
qemu-kvm-debuginfo-0.12.1.2-2.156.el6.x86_64
gpxe-roms-qemu-0.9.7-6.7.el6.noarch
qemu-kvm-tools-0.12.1.2-2.156.el6.x86_64
qemu-img-0.12.1.2-2.156.el6.x86_64
qemu-kvm-0.12.1.2-2.156.el6.x86_64

How reproducible:
rarely

Steps to Reproduce:
1.Boot up a guest 
2.Use dd to generate a file in guest and save md5 value
$dd if=/dev/zero of=/tmp/file_base bs=1M count=1000
$md5sum /tmp/file_base

3. shut dow guest and do convert or snapshot and rebase operate
$ qemu-img convert -f qcow2 -O qcow2 rhel6.1.qcow2 rhel6.1.qcow2_to_qcow2.qcow2

or
$qemu-img create -b rhel6.1.qcow2 -f qcow2 sn1.qcow2
$qemu-img create -b sn1.qcow2 -f qcow2 sn2.qcow2
$qemu-img rebase -b rhel6.1.qcow2 -F qcow2 sn2.qcow2

Between these steps in rebase, we will bootup guests and dd file in it. The md5 value changed file is the one that dd in sn2.qcow

4. boot up and check the md5
for convert
$md5sum /tmp/file_base
for rebase:
$md5sum /tmp/file_sn2

Actual results:
File changed
Expected results:
File should the same after and before these operate

Additional info: